Investigate forty only children (half of each sex), eighty first children, and eighty second children of two-child families. Half of the second and third children will have siblings of the same sex and half will have siblings of the opposite sex. Three clusters of variables believed to mediate the consequences of being an only child will be examined. These are: parental attitudes concerning family size and achievement; sibling and peer interaction; and family interaction and climate. Because only children will have different experiences than children with siblings relative to these three factors, it is expected that they will exhibit distinctive patterns of ego identity and reciprocal interaction skills.